The Effect of Iranian Customary Used Probiotic Yogurt on the Children's Salivary Cariogenic Microflora.

STATEMENT OF THE PROBLEM
Dental caries is the most common disease of childhood. Using probiotics has recently been introduced to reduce the incidence of dental caries.It consists of live microbial food supplements that beneficially affect the host, and hence are considered an alternative way to eradicate the infections.


PURPOSE
The aim of this study is to evaluate the effect of consumption of probiotic yogurt on the children's salivary cariogenic microflora.


MATERIALS AND METHOD
A double-blind randomized study was performed recruiting 2 parallel groups; 24 healthy children in the case and 25 children in the control group. All healthy children were followed- up over 4 periods. Periods 1 and 3 were wash-out periods with duration of 1 and 2 weeks, respectively. During periods 2 and 4 (2weeks duration each), the case group consumed 200g yogurt containing Bifidobacterium lactis (1×10(6) per gram) once daily and the control group consumed normal yogurt. Salivary Streptococci mutans and Lactobacilli were enumerated before and after the yogurt consumption periods. Pre- and post-treatment values within and between regimens were compared using the t-test and paired samples.


RESULTS
There was a reduction in Streptococcus mutans and Lactobacillus counts in the control group, but for Streptococcus mutans, the count reduction between phases 1 and 4 was statistically significant (p= 0.009). In the case group, neither the Streptococcus mutans count nor the Lactobacilli count was significantly reduced.


CONCLUSION
Based on the findings of this study, short-term daily consumption of probiotic yogurt containing Bifidobacterium lactis could not reduce the levels of salivary Streptococcus mutans and Lactobacilli in 6 to 12 year-old children, while normal yogurt could reduce the Streptococcus mutans counts significantly.


Introduction
Dental caries is the most common chronic disease affecting the majority of adults and 60-90% of school children. [1] Caries is a multifactorial disease with bacterial origin that can demineralize tooth enamel. [2] In dental caries, there is an increase in acidogenic and ac-id-tolerating species such as mutans Streptococci and Lactobacilli, although other bacteria can be found.
Changes in the homeostasis of the oral cavity would enhance proliferation of bacterial biofilm, notably mutans, from the streptococci group. [3] Streptococcus mutans is believed to play an impo-rtant role in the initiation of caries and Lactobacillus to have a part in the progression of tooth decay. [4] One of the methods that have recently been considered effective on the reduction of dental caries and decrement of cariogenic flora is the use of probiotic products. [5] Probiotics can promote oral health and also prevent oral diseases like caries, gingivitis, periodontitis and halitosis. The use of health promoting bacteria is one of the novel approaches in oral health. [5] The consumption of probiotics may have a favorable effect on the reduction of dental caries. [6][7] Several studies have shown that using the probiotic products could replace and ex-change the cariogenic bacteria with non-cariogenic ones. [8] These studies have employed different approaches. One approach is making use of the ability of probiotic bacteria to colonize on teeth and influence the supragingival plaque. [8] Probiotics must be able to attach to the surface of teeth and integrate into the bacterial population, making the dental biofilm. [5] The term probiotic, introduced by Gibson and Roberfroid, is a live non-digestible microbial food whose efficacy on human health has been established.
[6] A number of probiotic products that can play a critical role in human health have been proposed to have the potential to improve intestinal balance and influence the immune system through molecular mechanisms. [9][10][11] Other studies have investigated the application of probiotics in treating cardiovascular diseases, urogenital infections and cancer [12][13][14][15] but little attention is paid to its possible effect on oral health and risk factors of caries. The present study has focused on the effect of probiotics on oral microorganisms.   [19] In another study, Singh et al. (2011) showed that probiotic ice-cream could decrease the count of Streptococcus mutans, but its effect on Lactobacilli count has not been significant. [20] Regarding the findings of some studies that have demonstrated the probiotics to be useful in reducing the cariogenic flora of mouth and also the availability of probiotic yogurt, the present study is aimed to evaluate the effect of probiotic yogurt consumption on the cariogenic flora of children. We were also interested to explain whether the effect of probiotics would remain during the predefined four different periods.

Materials and Method
This randomized double-blind study recruited 49 healthy children with the age range of 6-12 years old (mean age=9.2±1.7) referred to the School of Dentistry, Shiraz University of Medical Sciences. Participants had not used any probiotic products. Those who were receiving Xylitol-containing products or fluoride treatments were excluded from the study. Using any fluoride products was forbidden.
Participants were instructed to brush their teeth twice a day and maintain their normal oral hygiene.
Using chewing gums containing Xylitol as well as probiotic yogurt during the study was forbidden. Any changes in health and using any medicine were considered. An experienced dentist examined the oral health of the participants before the study.
This study had two parallel groups; 24 healthy children in the case group and 25 healthy children in the control group. Both groups were matched on the following attributes: age, gender and DMFT. All of the children in the study were followed up over four periods.   Table 1 and 2.

Discussion
The findings of this study showed that short-term consumption of probiotic yogurt could decrease neither   nuing the administration of probiotic product prepared with this bacterium. [22] The results showed that Lactobacillus reuteri had not been colonized permanently in the oral cavity after a period of 2 weeks consumption.
In accordance with most studies conducted before, this study showed no reduction of salivary Lactobacilli prevention. [27] This assessment revealed that all studies were generally small or medium in sample size and majority of them (80%) were short-term interventions.
The quality of published papers recorded using the Consort score was 4 excellent, 9 good and 10 poor. These